Adhesive composition

ABSTRACT

An adhesive composition which comprises a mixture of (a) an unvulcanized elastomeric block copolymer having the general configuration A - B - A wherein each A is a nonelastomeric monovinyl aromatic hydrocarbon polymer block and B is an elastomeric conjugated diene polymer block, and (b) a compatible thermoplastic tackifying resin containing carbon-to-carbon unsaturation therein and derived from hydrocarbons selected from aliphatic and alicyclic hydrocarbons.

United States Patent [191 Downey Apr. 29, 1975 [54] ADHESIVE COMPOSITION3,509,239 4/1970 Tindall 260/876 B 3 P l. 26 [75] Inventor: Raymond E.Downey, Copley, Ohio 577398 5/197] ace at d 0/85 3 R [73] Assignee: TheGoodyear Tire & Rubber Company Akron, Ohio Przmary ExammerDonald E. Czaa Assistant ExaminerH. H. Fletcher [22] Filed: Sept- 5, 1974 Attorney,Agent, or FirmF. W. Brunner; H. C. 21 Appl. No.: 503,228 Young RelatedUS. Application Data [63] Continuation of Ser. No. 430,341, Jan. 2,1974,

abandoned, which is a continuation of Ser. No. [57] ABSTRACT 323,56l,Jan. 15, 1973, abandoned, which is a continuation of Ser. No. 169,853,Aug 6, 1971, An adhesive composition which comprises a mixtureabandoned. which is a continuation of Ser. No. of (a) an unvulcanizedelastomeric block copolymer 807975 March 9 abandonedhaving the generalconfiguration A B A wherein each A is a nonelastomeric monovinylaromatic hyl l 260/876 117/122 117/122 PF; drocarbon polymer block and Bis an elastomeric conll7/155 UA; 260/33-6 AQ; 260/888; 269/894 jugateddiene polymer block, and (b) a compatible [5 Clthermoplastic resincontaining carbon..to- Fleld of Search 260/876 3, 894 carbonunsaturation therein and derived from hydrocarbons selected fromaliphatic and alicyclic hydro- [56] References Cited carbons UNITEDSTATES PATENTS 3,239,478 3/1966 Harlan 260/876 B 3 Claims, No DrawingsADHESIVE COMPOSITION This is a continuation of application Ser. No.430,341 filed Jan. 2, 1974, which is a continuation of application Ser.No. 323,561 filed Jan. 15, 1973, which is a streamline continuation ofapplication Ser. No. 169,853 filed Aug. 6, 1971, which is a streamlinecontinuation of application Ser. No. 807,975 filed Mar. 17, 1969, allnow abandoned.

This invention relates to adhesive compositions and to methods for theirpreparation. While the invention is not restricted thereto, it hasparticular reference to pressure sensitive adhesives. It further relatesto pressure sensitive tapes.

Various adhesives can advantageously be used as pressure sensitive,laminate and hot melt adhesives. Most are generally known for theirability to form bonded laminated articles and some are more particularlyknown as pressure sensitive adhesives and some as hot melt adhesives.

Pressure-sensitive adhesives and adhesive-coated masking tapes and thelike are well known. These products commonly contain natural rubber anda thermoplastic tackifier resin compatible therewith. The adhesive,coated on a flexible backing to form a tape, is tacky at normal roomtemperatures and adheres instantly and tightly to surfaces against whichit is pressed without requiring moistening or heating. It typically isrequired to have good shear strength and 180 peel strength in order tobe commercially useful.

Heretofore, adhesive compositions have been prepared by mixingconjugated diene-monovinyl aromatic hydrocarbon block copolymers suchas, for example, polystyrene-polyisoprene-polystyrene block polymerswith tackifying resins containing aromatic substituents. However, formany applications such as pressure sensitive, laminating and hot meltadhesives, these adhesive compositions have insufficient tack to becommercially useful. In particular,-pressure sensitive tapes preparedtherefrom typically have had insufficient shear strength and 180 peelstrength, critical physical properties for most commerical tapes.

Therefore, it is an object of this invention to provide adhesivecompositions having improved adhesive properties and to provide a methodfor their preparation.

In accordance with this invention it has been found unexpectedly that anadhesive composition comprises a mixture of (a) an unvulcanizedelastomeric block copolymer having the general configuration A B Awherein each A is an independently selected nonelastomeric monovinylaromatic hydrocarbon polymer block having an average molecular weight of2,000 to 100,000 and a glass transition temperature above about 25C.,the total block A content being from about to about 50 percent by weightof the copolymer, and B is an elastomeric conjugated diene polymer blockhaving an average molecular weight from about 25,000 to about 1,000,000and a glass transition temperature below about 10C., said copolymerhaving a tensile strength at 25C. in excess of about 200 pounds persquare inch, and (b) a compatible, thermoplastic tackifying resincontaining carbon-to-carbon unsaturation therein and derived fromhydrocarbons having from 5 to 8 carbon atoms and at least onecarbon-to-carbon double bond therein selected from aliphatichydrocarbons and alicyclic hydrocarbons.

In the unvulcanized elastomeric block copolymer, it is preferred thatthe nonelastomeric monovinyl aromatic hydrocarbon polymer block is apolymer of styrene having an average molecular weight of from about5,000 to about 30,000, that the elastomeric conjugated diene polymerblock is a 1,4-addition polymer of a con- 5 jugated diene selected fromisoprene and 1,3-butadiene having an average molecular weight of fromabout 50,000 to about 150,000, and the total block A content is fromabout 10 to about 50 percent, more preferably from about 12 to about 30percent by weight of the copolymer. It is especially preferred that theelastomeric conjugated diene polymer block is a 1,4-addition polymer ofisoprene. The copolymer typically can have an intrinsic viscosity offrom about 0.6 to about 1.5 as determined by 0.5 grams in 50 millilitersof toluene solution at 30C.

In the practice of this invention the thermoplastic tackifying resinspreferably have a softening point according to ASTM Method E28-58T offrom about 50 to about 150C. and more preferably from about to about C.They are derived from aliphatic and alicyclic hydrocarbons, preferablyaliphatic hydrocarbons, and therefore contain essentially no unitsderived from aromatic hydrocarbons. In this regard it is preferred thatnot more than about 5 percent by weight of the units of the tackifyingresin are derived from aromatic hydrocarbons and more preferably it isdesired that none of the units are derived from aromatic hydrocarbons.Furthermore, it is preferred that the tackifyin g resin containscarbon-to-carbon unsaturation therein. Therefore, it is preferred thatat least a portion of the hydrocarbons used to prepare the resin have atleast two carbon-to-carbon double bonds therein. As an indication ofsuch unsaturation contained in the tackifying resin, it has been foundthat satisfactory resins having an iodine number according to ASTMMethod Dl959-61 of from about 40 to about 150.

Various thermoplastic tackifying resins can be used in this inventionsuch as, for example, resins derived by polymerizing unsaturatedhydrocarbons obtained from petroleum fractions and processes relatedthereto. It is usually desired to copolymerize at least one unsaturatedhydrocarbon having one double bond (monoolefin) with at least oneunsaturated hydrocarbon having more than one double bond (diolefin).Various mole ratios of diolefins to monoolefins can be used such as fromabout 20:80 to about 80:20. Representative of various diolefins arealiphatic diolefins having from 4 to 8 and preferably from 4 to 6 carbonatoms, particularly the conjugated dienes such as 1,3-butadiene,2-methyl- 1 ,3-butadiene (isoprene 2-ethyl- 1 ,3- butadiene and1,3-pentadiene (piperylene), and aliphatic cyclic diolefins such ascyclopentadiene and dicyclopentadiene. It is usually preferred that atleast one of the double bonds is alpha to the first carbon atom.Representative of various monoolefins are aliphatic monoolefins havingfrom 3 to 8, and preferably from 4 to 6, carbon atoms such as propylene,the various butenes, including 2-methyl-2-butene, the pentenes, thehexenes, the heptenes and the octenes, and cyclic aliphatic monoolefinshaving from 5 to 8 and preferably from 5 to 6 carbon atoms such ascyclopentene, cyclohexene, cycloheptene and cyclooctene.

The resins are generally prepared by polymerizing the unsaturatedhydrocarbons in an inert volatile solvent or diluent in the presence ofa suitable catalyst such as a Friedel-Krafts type catalyst, preferablyselected from aluminum chloride, aluminum bromide,

stannic chloride, boron trifluoride, boron trifluoride etherate and alsoalkyl aluminum halides such as isopropyl aluminum dichloride. Usually,for convenience, particulate anhydrous aluminum chloride is preferred.

In the preparation of the resins, a wide range of temperatures aresuitable for the polymerizations. For example, the polymerizations cannormally be carried out in the range of from about 20 to about 100C. andusually more preferably from about C. to about 50C. but above thefreezing point of the reaction system and below its boiling point.Certainly, whether the pressure at which the reaction is being conductedshould be taken into consideration when determining the optimumtemperature. Normally, the polymerization reaction pressures may beatmospheric or above or below atmospheric pressure. Generally, asatisfactory polymerization is conducted at about autogenous pressuredeveloped under the operating conditions used.

Exemplary of a preferred thermoplastic tackifying resin for thisinvention comprises from about 20 to about 80 units derived frompiperylene and correspondingly from about 80 to about 20 units derivedfrom 2-methyl-2-butene. The tackifying resin typically has a softeningpoint of from about 80 to about 1 C. The preparation of such a resinpolymer is more fully described in US. Pat. No. 3,577,398. Such a resinpolymer can be prepared, for example, by polymerizing a mixturecomprising from about 20 to about 75 weight percent of piperylene andfrom about 80 to about 25 weight percent of 2-methyl-2-butene in thepresence of an anhydrous catalyst selected from aluminum chlo ride,aluminum bromide, stannic chloride, and boron trifluoride at atemperature of from about 0 to about 50C. It is usually preferred toconduct the polymerization in an inert volatile organic solvent usingaluminum chloride having a mesh size of from about 50 to about 200 US.Sieve size as the catalyst. The resin polymers can be modified bycontaining up to about 25 percent by weight units derived frompiperylene dimers, piperylene trimers, and other unsaturatedhydrocarbons containing from 4 to 6 carbon atoms such as butene andsubstituted butenes such as 2-methyl-l-butene, 2,3-di-methyl-l-butene,2,3-dimethyl-2-butene, 3,3- dimethyl-l-butene; the pentenes andsubstituted pentenes such as l-pentene, Z-pentene, 2-methyl-lpentene,Z-methyl-Z-pentene, 3-methyl-2-pentene, 4-methyl-l-pentene;4-methyl-2-pentene, the hexenes such as 2-hexene, diolefins such asisoprene, and cyclic unsaturated hydrocarbons such as cyclopentene,cyclohexene and 1,3-cyclopentadiene.

The unvulcanized elastomeric block copolymer used in this inventioncomprises nonelastomeric terminal polymer blocks and internalelastomeric polymer blocks. The characteristics of the internal ormiddle block, which is elastomeric, may be that expressed in ASTMSpecial Technical Bulletin No. 184 as follows: A substance that can bestretched at room temperature to at least twice its original length and,after having been stretched and the stress removed, returns with forcedto approximately its original length in a short time.

The terminal nonelastomeric blocks constitute polymeric blocks which donot meet this definition. Furthermore, the difference between glasstransition temperatures of the end blocks and middle blocks should be atleast 40C. and preferably at least 100C.

Typically, the unvulcanized elastomeric copolymers can be prepared byfirst polymerizing olefins such as ethylene, propylene, styrene,polymethyl styrene, methyl styrene, acrylonitrile, chlorostyrene andmethyl methacrylate with a lithium based initiator. A suitable lithiumbased initiator is, for example, lithium metal, alkyl lithium compounds,lithium hydrocarbyls and organo lithium amides. The alkyl-lithiumcompounds are preferred. Particularly preferred alkyl lithium compoundsare branched chain, preferably secondary alkyl lithiums. Such alkyllithium compounds especially include secondary butyl lithium, isobutyllithium, isoamyl lithium and secondary amyl lithium.

After polymerizing this monomer to an average molecular weight of fromabout 2,000 to about 100,000, and preferably from about 5,000 to about30,000, a conjugated diene and additional amounts of the first monomerare added to the polymerization mixture. Preferred conjugated dienes arealiphatic conjugated dienes such as isoprene, methyl isoprene,butadiene, copolymers of the styrene-butadiene type andbutadiene-acrylonitrile.

The polymerization then continues to provide an elastomeric middle blockpolymer of the conjugated diene having an average molecular weight offrom about 25,000 to about 1,000,000, and more preferably between about50,000 and about 500,000, followed by a non-elastomeric block polymer ofthe original type of monomer.

Typically, the preparation of the elastomeric block copolymer is made bypolymerizing the monomers at temperatures in the order of about 20C. toabout 100C., preferably between about 20 and about 65C. in an inerthydrocarbon solvent such as an alpha olefin or aromatic hydrocarbon.Typically inert hydrocarbon solvents are aliphatic hydrocarbons(including cycloaliphatic) such as cyclohexane and a typical aromatichydrocarbon is benzene. Usually the amount of initiator should bemaintained as low as possible, but may be varied over a relatively widerange such as from about 1 to about 200 parts per million, based on theweight of the monomers present.

In the practice of this invention adhesive compositions are prepared bymixing the elastomeric block copolymer with the tackifying resins in thepresence of volatile organic hydrocarbon solvents at varioustemperatures such as from about 0 to about 100C. and typically fromabout 20 to about 60C. but above the freezing point of the mixture andbelow its boiling point. Various aliphatic and aromatic hydrocarbons canbe used. Representative examples of such aromatic hydrocarbons aretoluene and benzene and representative examples of aliphatichydrocarbons are pentane, hexane, heptane and octane. A particularlysuitable hydrocarbon solvent is a mixture containing from about 10 toabout parts of toluene and correspondingly from about 90 to about 10parts of hexane. This adhesive mixture is then suitable for bondingsubstrates such as by simply applying it to'the substrate surfaces,partially drying it, and contacting the said substrate surfaces with theadhesive mixture therebetween and drying the said adhesive.

The mixture has particular utility as a pressure sensitive adhesive. Forexample, pressure sensitive tapes can easily be prepared by applying thesolution of the adhesive mixture to a flexible substrate and drying themixture. The adhesive of this invention also has utility as a hot meltpressure sensitive adhesive, particularly when prepared by mixing theelastomeric block copolymer, the hydrocarbon tackifying resin and aminor amount of an oil such as a petroleum derived or coal tar derivedoil. Particularly suitable is mineral oil. The hot melt adhesive issimply applied by heating the mixture, applying it to a substrate andcooling. After cooling it is surprisingly found that the adhesive hasgood pressure sensitive properties.

In the preparation of the adhesives of this invention it is understoodthat minor amounts of various antioxidants and fillers can be added andmixed therewith in order to further improve its aging characteristicsand various physical properties.

The following examples further illustrate the invention and are notintended to be limiting. In these examples the parts and percentages areby weight unless otherwise indicated.

EXAMPLE 1 Component PerCcnt 2-pentcne 5.1 2-methyl-2-butcnc 32.9lsoprcnc 3.1 1.3-pcntadicne (piperylcne) 27.5 2,3-dimethyl-l-butene 2.l4-methyl2-pentene 19.4 Unsaturated hydrocarbons containing 5 to 6 carbonatoms 10.5

After this polymerization, 25 parts of water, 8 parts of particulatehydrated calcium hydroxide and 8 parts of Attapulgus clay were added tothe poly'merizate. Agitation was provided to suspend the hydratedcalcium hydroxide at about 90C. and continued for about 120 minutes. Themixture was then filtered to remove the insoluble catalyst residue,excess calcium compound and clay. The filtrate was then steam distilledto a pot temperature of about 235C. The resulting residual molten resinwas poured from the reactor onto an aluminum tray and cooled to about25C. to form 173 parts of a hard brittle resin having a pale yellowcolor, and having a softening point, according to ASTM Method E28-58T of94C.

EXAMPLE 11 A polystyrene-polyisoprene-polystyrene unvulcanizedelastomeric block copolymer was prepared by the following method:

A solution was prepared consisting of 2 grams of styrene in a 20milliliter solution of benzene. The solution was run through silica gelat about 25C. to remove trace amounts of water and then sparged with drynitrogen for about 30 seconds to remove trace amounts of air.

To the solution was added 0.2 millimoles of secondary butyl lithium in a0.3 molar heptane solution. The mixture was allowed to polymerize andset aside for about 16 to 18 hours at about 25C.

A solution was prepared consisting of 16 grams of isoprene and 2 gramsof styrene in 80 milliliters of a benzene solution. The solution was runthrough silica gel at about 25C. to remove traces of water and spargedwith dry nitrogen to remove trace amounts of air.

The mixture of isoprene, styrene and benzene was mixed with the originalpolymerized styrene mixture to the exclusion of air in a reactor. Thereactor was sealed and placed in a heated liquid polymerization bath atabout 50C. for about 4 hours until about a 100 percent completion of thepolymerization occurred.

The resulting polymer was coagulated with methyl alcohol containing avery small amount of a phenolic antioxidant and dried. The resultingpolymer had an intrinsic viscosity of 1.12 in toluene at 30C. Itcontained 18 percent by weight units derived from styrene.

A portion of the polymer was molded in the form of dumbbells at 138C.The dumbbells had a thickness of 0.6 inches, a width of 0.1 inches atits narrow portion and a length of 0.8 inches. The dumbbells were testedon an lnstron tester at 25C. with a crosshead separation speed of 2inches per minute. The tests indicated that the prepared block copolymerhad an ultimate tensile strength of about 250 pounds per square inch atan elongation of 1,500 percent.

Analyses indicated that the block copolymer had a molecular weight ofabout 100,000. Thus, assuming that the terminal polystyrene blocks wereof equal molecular weight, the block copolymer comprised terminalpolystyrene blocks having molecular weights of about 9,000 and internalpolyisoprene having a molecular weight of about 82,000.

EXAMPLE 111 Mixtures of various tackifying resins with apolystyrene-polyisoprene-polystyrene block copolymer, obtained as Kraton107 from The Shell Chemical Company, were prepared. The block copolymerwas similar to the copolymer prepared according to Example 11. Itcontained about 12 percent styrene by weight, a glass transitiontemperature of about C. and a tensile strength of about 1,200 pounds persquare inch with an elongation of about 1300 percent measured at 25C.,according to the method used in Example 11. The copolymer had anintrinsic viscosity of 1.1 as measured in toluene at 30C.

The mixtures of tackifying resin and block copolymer were prepared bythe following method:

One part of an amine type of non-staining antioxidant was dissolved in300 parts of a hydrocarbon solvent at about 25C. The hydrocarbon solventconsisted of 20 parts of toluene and parts of hexane. This mixture ofhydrocarbons was used for the solvent to provide an optimum viscosityfor sample preparation. To the solvent mixture was added parts of theblock copolymer of polystyrene-polyisoprene-polystyrene and 100 parts ofa tackifying resin. The mixture was agitated by rolling in a containerat about 25C. for about 8 to 12 hours.

The mixture was coated onto a polyester film having a 1 mil thickness(obtained as Mylar from The E I du- Pont deNemours and Company) with adoctor blade to provide a I ml coating on the polyester film. Thecoating was allowed to partially dry at about 25C. for about 2 minutes.The polyester film with the coat thereon was then placed in a hot airoven having a temperature of 70C. for about minutes. The sample wasremoved from the hot air oven and allowed to cool to about C. and, forprotective purposes, a release paper was placed over the coating. Therelease paper was a clay coated sheet of paper with a silicone releaseagent overcoat. The sample was cut into strips one inch wide for testingpurposes. The results of 180 peel strength and shear strength tests bothon freshly prepared samples and on samples allowed to age at 70C. forabout 5 days are shown in the following table:

In this example the 180 peel strength tests were conducted according toMethod PSTC-l. revised in April of I966, of the Pressure Sensitive TapeCouncil. This method is found in the Fifth Edition of TEST METH- ODS FORPRESSURE SENSITIVE TAPES" developed by the Pressure Sensitive TapeCouncil, I201 Waukegan Road, Glenview, Illinois. This test measures theaverage pull value required to peel the adhesive from the substrate at a180 angle in pounds per one inch width of the test sample. The shearstrength was measured in this example according to the method describedas PST-7 of the Pressure Sensitive Tape Council. In particular, it wasmeasured by applying a 1,000 gram weight to the sample and measuring thetime required for the tape to separate from the substrate. For

the purposes of this example a time of about 5 days was used.

Table 1 Sam- Tackifying Iodine l80 Peel Strength (lbs) Shear Strengthple Resin No. Fresh After Fresh After No. Origin (I Sample Aging SampleAging l Aliphatic Hy- 70-l l0 3.5 4.0 No No drocarbons (2) FailureFailure 2 Aliphatic Hy- I 3.7 3.3 No No droearbons (3) Failure Failure 3Aliphatic Hy- 44 2.5 1.5 No No.

drocarhons (4) Failure Failure 4 Styrenated 92 None None None None Resin(5) 5 Styrcne-Acrylo- None None None None nitrile (6) 6 Aromatic Hy-None None None None drocarbons (7) 7 Styrene, Vinyl None None None NoneToluene (8) 8 Styrene (9) None None None None (I) According to ASTMMethod D-l959-6l. (2) Prepared according to the method of Example I. (3)Obtained as Piccopale SF-IOO from The Pennsylvania Industrial ChemicalsCompany. (4) Obtained as Piccopale H-2, a hydrogenated resin. from ThePennsylvania Industrial Chemicals Company. (5) Obtained as Nevex fromThe Neville Chemical Company. (6) Obtained as Piccoflex I00 from ThePennsylvania Industrial Chemicals Company. (7) Obtained as Picco 6l00from The Pennsylvania Industrial Chemicals Compan (8) Obtained asPiccotex I00 from The Pennsylvania Industrial Chemicals Company. (9)Obtained as Piceolastic A75 from The Pennsylvania Industrial ChemicalsCompany.

Table 2 Samp Resin l80 Peel Shear No. Parts Strength (lbs) Strength 9 602.8 No failure I0 I00 2.6 48 hours ll I50 4.8 No failure I 200 3.8 Nofailure In Samples I-3, 9 and l 1-l2, all of the samples exhibited peelstrength to be suitable as a pressure sensitive adhesive. In Samples 4-8none of the samples indicated a measurable peel strength.

In Samples 1-3 the shear strength test indicated no failure after about5 days. In Sample 10 the shear strength test indicated a failure after48 hours for the hot melt pressure sensitive adhesive. Such a shearstrength for the adhesive is adequate and suitable for a pressuresensitive adhesive. In Samples 4-8 the shear strength indicated analmost immediate failure.

As indicated, the adhesive composition of this specification can besuitable for preparing a hot melt pressure sensitive adhesive. When itis used as such an adhesive, generally up to about 30 percent by weightand more preferably from about 5 to about 20 percent by weight of anoil, such as a rubber processing oil, is mixed with the composition.Suitable processing oils are normally derived from petroleum, althoughthey can also be derived from coal tar and other sources such as rosinoils. Representative processing oils are more fully described in US.Pat. No. 3,081,276. The processing oils are usually composed primarilyof paraffmic hydrocarbons, naphthenic hydrocarbons and aromatichydrocarbons. Such oils are well-known commercial oils normally used inrubber compounding which are generally high-boiling petroleum fractionsobtained after gasoline, fuel oil and other lower boiling materials areremoved by distillation. They normally have a viscosity of from about 10centipoises at 100C. up to semisolid materials softening at about 40 toabout 90C. They usually have a boiling point of from about 50C. to atleast about 200C. and higher. For example, many processing oils have aboiling point of at least about 245C. at 10 millimeters of mercury. Theynormally have a specific gravity (60/60F.) of from about 0.9 to about1.05.

As indicated, the adhesive composition has particular utility as apressure sensitive adhesive. In this regard, commercially usefulpressure sensitive tapes are provided comprising the adhesivecomposition adhered to a flexible substrate. Certainly, variousconventional substrates, or backings for such tapes, can be used.Representative examples of such substrates are paper, cloth and variousnonfibrous films such as cellophane, vinyl resins, polyethylene and thelike. In the preparation of pressure sensitive adhesive tapes, theadhesive composition can be applied in various conventional manners suchas from a solvent solution or dispersion using the hydrocarbon solventsindicated herein. Typical conventional methods of applying the adhesivecomposition include the use ofa hot melt spreader, calendar, reverseroll coater, knife or doctor blade.

1n the practice of this invention various amounts of the tackifyingresin can be mixed with the copolymer to provide the adhesivecomposition, depending somewhat upon its intended use. For example,useful adhesive compositions are prepared by mixing from about 30 toabout 250 percent by weight of the tackifying resin with the copolymer.More particularly, in pressure sensitive adhesive applications it ispreferred that the tackifying resin comprises from about 30 to about 200percent by weight of the copolymer; in hot melt ad- 4 While certainrepresentative embodiments and details have been shown for the purposeof illustrating the invention, it will be apparent to those skilled inthis art that various changes and modifications may be made thereinwithout departing from the spirit or scope of the invention.

1 claim:

1. A pressure sensitive adhesive composition which consists essentiallyof a mixture of a. an unvulcanized elastomeric block copolymer ofstyrene and isoprene having an intrinsic viscosity of about 0.6 to about1.5 as determined by 0.5 gram in 50 milliliters of toluene solution at30C and having the general configuration A B A wherein each A is anindependently selected nonelastomeric styrene polymer block having anaverage molecular weight of about 5,000 to about 30,000 and a glasstransition temperature above about 25C, the total block A content beingfrom about 10 to about 50 percent by weight of the copolymer, and B isan elastomeric 1,4 addition polymer block of isoprene having an averagemolecular weight from about 50,000 to about 150,000, a tensile strengthat 25C in excess of 200 pounds per square inch, and a glass transitiontemperature below about 10C, the difference between the glass transitiontemperatures of the A and B blocks being at least 40C, and

(b) from about 30 to about 250 weight percent based on the blockcopolymer of a compatible, thermoplastic tackifying resin containingcarbon-tocarbon unsaturation therein, comprising from about 20 to aboutpercent units derived from piperylene and correspondingly about 80 toabout 20 percent units derived from 2-methyl-2-butene, having asoftening point of about 80 to about 1 10C, having an iodine number offrom about 40 to about according to ASTM D 1959-61, derived frompolymerizing with aluminum chloride a mixture comprising piperylene and2-methyl-2- butene in a mole ratio of about 20:75 to about 75:20, andhaving a maximum of about 5 weight percent of an aromatic component.

2. The adhesive composition of claim 1 where the I tackifying resincomprising the copolymer of piperylene and 2-methyl-2-butene is modifiedby containing up to about 25 percent by weight units derived from thegroup consisting of piperylene dimers, piperylene trimers and otherunsaturated hydrocarbons containing from 4 to 6 carbon atoms.

3. A pressure sensitive tape comprising the adhesive composition ofclaim 1 adhered to a flexible substrate.

1. A PRESSURE SENSITIVE ADHESIVE COMPOSITION WHICH CONSISTS ESSENTIALLYOF A MIXTURE OF A. AN UNVULCANIZED ELASTOMERIC BLOCK COPOLYMER OFSTYRENE AND ISOPRENE HAVING AN INTRINSIC VISCOSITY OF ABOUT 0.6 TO ABOUT1.5 AS DETERMINED BY 0.5 GRAM IN 50 MILLILITERS OF TOLUENE SOLUTION AT30*C AND HAVING THE GENERAL CONFIGURATION A - B - A WHEREIN EACH A IS ANINDEPENDENTLY SELECTED NON-ELASTOMERIC STYRENE POLYMER BLOCK HAVING ANAVERAGE MOLECULAR WEIGHT OF ABOUT 5,000 TO ABOUT 30,000 AND A GLASSTRANSITION TEMPERATURE ABOVE ABOUT 25*C, THE TOTAL BLOCK A CONTENT BEINGFROM ABOUT 10 TO ABOUT 50 PERCENT BY WEIGHT OF THE COPOLYMER, AND B ISAN ELASTOMERIC 1,4 ADDITION POLYMER BLOCK OF ISOPRENE HAVING AN AVERAGEMOLECULAR WEIGHT FROM ABOUT 50,000 TO ABOUT 150,000, A TENSILE STRENGTHAT 25*C IN EXCESS OF 200 POUNDS PER SQUARE INCH, AND A GLASS TRANSITIONTEMPERATURE BELOW ABOUT 10*C, THE DIFFERENCE BETWEEN THE GLASSTRANSITION TEMPERATURES OF THE A AND B BLOCKS BEING AT LEAST 40*C, AND(B) FROM ABOUT 30 TO ABOUT 250 WEIGHT PERCENT BASED ON THE BLOCKCOPOLYMER OF A COMPATIBLE, THERMOPLASTIC TACKIFYING RESIN CONTAININGCARBON-TO-CARBON UNSATURATION THEREIN, COMPRISING FROM ABOUT 20 TO ABOUT80 PERCENT UNITS DERIVED FROM PIPERYLENE AND CORRESPONDINGLY ABOUT 80 TOABOUT 20 PERCENT UNITS DERIVED FROM 2-METHYL-2BUTENE, HAVING A SOFTENINGPOINT OF ABOUT 80* TO ABOUT 110*C, HAVING AN IODINE NUMBER OF FROM ABOUT40 TO ABOUT 140 ACCORDING TO ASTM D 1959-61, DERIVED FROM POLYMERIZINGWITH ALUMINUM CHLORIDE A MIXTURE COMPRISING PIPERYLENE AND2-METHYL-2-BUTENE IN A MOLE RATIO OF ABOUT 20:75 TO ABOUT 75:20, ANDHAVING A MAXIMUM OF ABOUT 5 WEIGHT PERCENT OF AN AROMATIC COMPONENT. 2.The adhesive composition of claim 1 where the tackifying resincomprising the copolymer of piperylene and 2-methyl-2-butene is modifiedby containing up to about 25 percent by weight units derived from thegroup consisting of piperylene dimers, piperylene trimers and otherunsaturated hydrocarbons containing from 4 to 6 carbon atoms.
 3. Apressure sensitive tape comprising the adhesive composition of claim 1adhered to a flexible substrate.